Mold for casting ingots of steel or other metals



Nov. H, 1930. A. G. E. HULTGREN MOLD FOR CASTING" INGOTS OF STEEL OR OTHER METALS 1929 2 Sheets-Sheet 1 Filed Feb. 11

.73 w de? Nov. M, 1930. A. G. E. HULTGREN MOLD FOR CASTING INGOTS OF STEEL OR OTHER METALS Filed Feb. 11, 1929 2 Sheets-Sheet 2 IIIIAWIAdWA/lllIl/IIIIJW la Fur Ilium? Patented Nov. 11, 1930 UNITED STATES PATENT OFFICE MOLD FOR CASTING- INGOTS OF STEEL OR OTHER METALS I Application filed February 11, 1929, Serial No. 339,119, and in Sweden February 22, 1928.

structure of a metal ingot largely depends on the rate of cooling during freezing: rapid cooling induces a finegrained structure. Various means have been em loyed in order to accelerate the freezing, or instance increasing the thickness of the mold, using a double-walled water-cooled mold, et cetera. However, such measures have proven not to be very efficient, because shortly after a solid shell of metal has formed this will contract,

as it cools further, and, where efiicient watercooling is not resorted to, the mold itself rapidly expands, as it is heated by the hot metal. From both causes an annular space is soon formed between ingot and mold, with the result that the transfer of heat from the former to the latter is considerably retarded.

The object of the present invention is to preserve contact between the ingot surface and the mold during freezing so as to ensure rapid freezing and, in consequence, the formation of a finegrained structure in the ingot. This is accomplished in the following manner. The mold, the cavity of which has a downward taper, has a detachable bottom. This bottom, being securely attached to the mold proper While the metal is poured, is then, at a suitable moment, lowered so as to allow the ingot to sink in the mold, resting in the taper of the latter and gliding downwards as fast as contraction of ingot and expansion of mold proceeds.

The close contact between ingot and mold is further improved by the high surface pressure resulting from the wed ging action of the taper. The mold bottom, after being detached, is preferably supported by a spring or lever in such a manner that an upward pressure is applied equal to or exceeding its 4.0 weight so as to ensure continued contact with the bottom surface of the ingot.

The invention is illustrated in the accompanying drawings, where Figure 1A shows a mold constructed according to an embodiment of the invention,

in vertical section, and Figure 1B shows thesame mold seen from outside and from left in Figure 1A.

Figure 2 shows a modification of the body of the mold in vertical section.

Figure 3 shows in vertical section a mold according to Figure 1 provided with means for external cooling.

' Figure 8 is a plan view showing a detail.

Figure 4 is a vertical section showing in two different planes a second embodiment of the mold.

Figure 5 is a vertical section showing a modification of the embodiment according to Figure 4:. n Figure 1 the ingot is marked by 1, and 2 is the mold with its loose bottom 3. The latter is rovided with an exchangeable plug 3. 4: is the feedin box. The mold rests on the frames 5. While the metal is poured, the mold bottom 3 is securely attached to the mold 2 by means of two hoops 6 with keys 7 engaging in ears 8 in the mold and 9 in the bottom. After the keyings are detached, the bottom is supported by the spring 10 the pressure of which is preferably ad uSted to exceed the Weight of the loose bottom. Thus the ingot is free to sink as the contraction of it and the expansion of the mold proceed. Ordinarily the bottom should not be loosened, until a shell of frozen metal has formed, of sufficient thickness to carry the fluid metal within. The loosening may, of course, be deferred to a later moment, if desired. The resistance against the sinking of the ingot consists of the spring pressure in excess of the weight of the bottom and the friction between the ingot sides and the mold wall. The former may be adjusted as desired; the latter is small, when the mold surface is smooth and, as is usually and preferably the case, coated with tar, soot, graphite or the like.

In Figure 2 a special embodiment of the mold is illustrated, the inner longitudinal profile of the mold being concave. The object hereof is explained as follows. Owing to the taper of the ingot the lower portion cools and contracts faster than the upper portion. If the taper is straight as shown in Figure 1, the surface of the loosened ingot will thus tend to leave the interior surface of the mold at the lower, while engaging it at the upper end. By the use of a concave profile, as shown in Figure 2, this efiect may be eliminated. Obviously, the

taper may be varied along the ingot in such a manner that the contact is limited to the lower portion in order particularly to accelerate the cooling of the latter, during any period of the solidification when such acceleration may be desirable.

Figures 3 and 3* illustrate means for accelerated cooling, the mold being watercooled externally. 11 is a water-pipe provided at the top or at any desired height and running round the mold, said pipe being provided with numerous holes. The water flowing along the outer surface of the mold collects at the bottom in channels 21, from where it is discharged. Such cooling being used, the mold may be provided with thinner walls than is else preferable, as not being subjected to so high a temperature.

In Figure 4 an embodiment of the invention is shown in which both the mold body 2 and the bottom 3 are double-walled for water-cooling. The water chambers 12, 13 are provided with inlet and outlet pipings. At the bottom 3, at least, the said pipings consist of flexible tubes 14 which without noteworthy resistance allow the bottom to sink preserving contact-with the underside of the ingot. In this case the weight of the bottom is balanced by means of lever 15 and'counter-weight 16.

In Figure 5 the inside wall of the doublewalled mold body 2 is made in a particular piece 17 in order to be made of a metal with good heat conductivity, for instance copper, and to be exchangeable. The inside wall 17 is outwardly provided with a helical rib 1 answering to a corresponding helical rib 1 on the inside of the outside wall. By means ing of the ingot after initial peripheral curred, and releasable means for securing said bottom against the mold body durlng said initial peripheral freezing of the ingot.

3. A mold body having a downwardly tapered ingot casting cavity, a depressible initial peripheral freezing has occurred, and

releasable means for supporting said bottom against depression during said initial peripheral freezing of the ingot.

4. A mold body having a downwardly tapered ingot casting cavity, said body having a double wall around said cavity providing a chamber fol-water to rapidly eliminate heat, said chamber having a water inlet and an outlet, a depressible bottom for said cavity adapted to allow sinking of the ingot after initial peripheral freezing to maintain contact between the ingot and the inner wall ofthe mold, and releasable means for supporting said bottom whilesaid initial peripheral freezing occurs. 5. A structure as specified in claim 4, in which the inner and outer mold walls are separately formed and provided with helical ribs co-acting with each other. in defining a water channel from said inlet to said outlet, said inner wall being formed from material which will rapidly conduct heat.

In witness whereof, I have hereunto signed my name.

AXEL GUSTAF EMANUEL HULTGREN.

freezing has occurred, thereby maintaining contact between the mold and the ingot, releasable means for securing said bottom against the mold during said initial peripheral freezing of the ingot, and yieldable means for supporting said bottom after release of said releasable means, said yieldable means exerting an upward force greater than the downward force exerted by the weight of the bottom but materially less than the downward force exerted by the weight of the ingot.

2. A mold body having an ingot casting cavity which tapers downwardly along the concave profile, a depressible bottom for said cavity adapted to allow sinking of the ingot after initial peripheral freezing has pc- 

